Abstract: Surface subsidence in coal mining areas is a critical geological hazard that severely disrupts socio-economic order and damages the local ecological balance. Grouting into bed separations within overlying strata is a forefront technology for controlling subsidence at its source in mining operations. Determining appropriate values for key grouting parameters, such as slurry material properties, injection-to-mining ratio, and water-cement ratio, is central to ensuring the desired effectiveness of subsidence control. To enable the synergistic optimization and quantification of parameters like slurry properties, this study proposes a surface settlement prediction model that accounts for the coupled control effects of multiple downstream grouting parameters. The model explores the synergistic and feedback-driven evolution between key parameters themselves and their relationship with surface settlement, ultimately identifying optimal grouting parameter combinations. The scientific accuracy of the theoretical model was tested via a self-developed, multi-field coupled, visual physical similarity simulation grouting system designed for bed separation grouting control experiments, followed by engineering application. Key findings are: A surface settlement prediction model considering the coupled control effects of multiple downstream grouting parameters was developed. Combined with the actual conditions of the study area’s working face, a key parameter combination satisfying the engineering control target under given conditions was identified: “Grade II fly ash + a water-cement ratio of 1.2∶1 + an injection-to-mining ratio of 0.48”. A subsidence control test was conducted using the self-developed system. When the working face advanced to 130.0 cm, the target layer at 109.0 cm above the coal seam roof developed the No. 7 separation space, while the water pressure during pre-grouting water testing entered a stable, constant-pressure phase, indicating the theoretical injection timing. The maximum macroscopic slurry diffusion radii for holes ZJ-01 and ZJ-02 were 238.7 mm and 294.5 mm, respectively. Contour maps confirmed an effective overlapping coverage zone between the holes, with structural controls leading to heterogeneous slurry distribution forming reinforced and weak zones. The test recorded a maximum surface settlement of 334.2 mm and a maximum settlement of 143.2 mm on the side of the stopping line, both meeting the control target (< 360.0 mm). An engineering application was implemented using a grouting scheme based on the key parameter combination from the theoretical model. During the monitoring period, the maximum surface settlement on the stopping line side was 122.8 mm, and the maximum subgrade settlement along the traffic artery was 243.9 mm, both achieving the control target. This verified the core effectiveness of the grouted layer in stabilizing the strata structure during the critical period, thereby effectively safeguarding the safety and stability of surface structures.